The tension forces on a wire being wound in a winding system for electrical coils must be kept constant at a preselected value. This is typically accomplished by disposing an automatic wire tension regulator between a wire supply roll and the coil-winding device. The demands on a wire tension regulator of this type are diverse, because the wire tension can fluctuate drastically during coiling due to the shape of the coil, which can be round, square, rectangular, oval, and so on. Also, wire tension can be affected by the increasing diameter of the coil during winding. During winding, it must also be taken into account that because of the technology and techniques used, the wire speed can also assume negative values, for example. The rapid effectiveness of the wire tension regulator is especially important, because delays caused by inertia can create uncontrollable wire-tension conditions that can greatly reduce the quality of the finished coil.
With conventional wire tension regulators, tension control is effected by mechanical means, electro-mechanical means, or some combination of these two. For example, tension control can be effected by a wire compensation arm that is associated with a potentiometer, if necessary.
Devices of this type have great disadvantages caused by inertia, particularly by after-running or braking of the wire during a negative wire speed occurring momentarily, and because of undesired oscillations of the wire compensation arm.
A device for controlling the tension of a wire being wound into an electrical coil is known from DE-OS 40 35 862. The device disclosed therein provides improvements by automatically controlling the wire tension and wire braking. The device comprises a preliminary brake formed by two felt-covered rollers. One of the rollers is permanently driven by a synchronous motor in a direction opposite to the feed direction of the wire. The other roller is carried along by the driving motor as a pad roller. The prestressed wire is guided at least 360.degree. around a grooved roller driven by an additional motor in the forward and return directions of the wire. The grooved roller is connected to a counter which counts the revolution rate of the grooved roller and produces a signal, which a control unit uses to control the motor. A tensiometer produces a signal representative of the wire tension, which is compared to a set value. The resulting signal is superimposed onto the signal from the counter to produce a control signal which is sent to and affects the operation of the control unit. The change in wire tension influences the signal, and the speed of the motor is altered to suppress this change in tension.
At higher pulling speeds, the quality of the wound coil is adversely affected at a high wire speed by differences occurring in tension. To counteract the delays caused by inertia, the winding wire is fed over a spring-mounted pivoting arm. The winding wire then runs across a roller provided with an encoded disk for making the appropriate corrections to the counter signal by means of an additional control device.
A disadvantage that is associated especially with multiplex winding machines is that the spring force of the pivoting arm must be adapted individually for each winding position in each winding operation according to the type and thickness of the wire. Tension control of this type is less suitable for particularly thin winding wires that are wound at high pulling speeds and for which the frictional force alone is of importance.